This invention relates to a method for avoiding the triggering of Type 1 diabetes in humans by the ingestion of milk or milk products. More particularly, the method relates to the selection of milk which does not contain a diabetogenic factor by selecting cows producing milk which contains any variant of xcex2-casein which does not stimulate diabetogenic activity in humans (a non-diabetogenic variant) to the exclusion of any variant of xcex2-casein which does stimulate diabetogenic activity in humans (a diabetogenic variant).
Type 1 diabetes occurs in individuals who are genetically susceptible. However, even in identical twins, diabetes may occur in one and not in the other. The present invention relies upon the discovery of an environmental trigger for Type 1 diabetes which operates very early in life.
The evidence that this environmental trigger is to be found in cows milk is based on epidemiological (Leslie et al, 1994), ecological (Virtanen et al, 1993) and animal experimental evidence (Elliott and Martin, 1984 and Elliott 1992). The diabetogenic factor of the milk appears to be in the casein fraction (Elliott et al, 1992), at least in the non-obese diabetic (NOD) mouse. Whey protein does not appear to, contain any diabetogenic component (Elliott et al, 1992). It has been suggested that bovine serum albumin (BSA), a protein found in the whey fraction of cows milk is the diabetogenic component of cows milk (Sheard, 1993). However, a review of the evidence supporting this theory does not indicate that BSA was ever tested for diabetogenic activity in the absence of xcex2-casein.
International PCT Application WO95/10537 discloses a method of producing denatured bovine serum albumin milk products. It is stated that the consumption of denatured BSA milk products tends to reduce the likelihood of a person acquiring type 1 diabetes. However, there is no evidence presented of any trials where either human or animal subjects were fed milk or milk products with denatured BSA. It relies upon the theory mentioned above that BSA is the diabetogenic component of cows milk (Sheard, 1993). In European Patent Application 629,350 there is described a method of hydrolysing cows milk protein to produce a hydrolysates substantially free of allergenic proteins. The hydrolysate also is suggested to be useful in the prophylaxis and treatment of type 1 diabetes melitis in children susceptible to such disease. In the description on page 6 of that specification it is suggested that BSA may be a trigger to the immune system. However, there are no examples in the patent specification and no reference to any papers showing any direct evidence of this suggestion.
In South African patent specifications 61/1804 laid open on Jun. 28, 1961, 61/2068 laid open on Sep. 20, 1961 and 62/600 laid open on Jul. 4, 1962 there are described compositions alleged to be cures for diabetes. There are no examples of any trials in support of these assertions. The compositions consist of casein as a base and fruit and leaves of South Africa plants. It is inferable from the description that the active ingredient is the plant material and there is no mention that casein has any role in causing or curing diabetes.
We have now tested the A1 and A2 variants of xcex2-casein and a whey protein on NOD mice and found that the A1 variant does have diabetogenic activity while the A2 variant and whey protein do not show diabetogenic activity.
It is an object of one aspect of the invention to use this finding to go some way to selecting milk and milk products which do not contain a diabetogenic factor in such milk or milk product or at least to offer the public a useful choice.
It is an object of another aspect of this invention to go some way towards selectively breeding cows and bulls whose offspring produce milk which is not diabetogenic or which at least offers the public a useful choice.
Accordingly, the invention may be said broadly to consist in a method of selecting milk for feeding to diabetes susceptible individuals which comprises testing milk from identified cows for the presence of variants of xcex2-casein and selecting those cows whose milk contains any non-diabetogenic variant and does not contain any diabetogenic variant, and milking separately the non-diabetogenic variant milk producing cows and recovering and maintaining their milk separately from milk from any other source.
Preferably said non-diabetogenic variant is the A2 variant of xcex2-casein.
Alternatively said non-diabetogenic variant is the A3, D or E variant of xcex2-casein.
Preferably said diabetogenic variant is the A1 variant of xcex2-casein.
Alternatively, said diabetogenic variant is any one of the B, C and F variants.
Preferably, said recovered milk is tested for the presence of any diabetogenic variant and discarded if any is found.
Alternatively, said method of testing comprises the use of mass spectrometry.
In one embodiment said mass spectrometry comprises electro spray ionisation mass spectrometry.
Alternatively, said mass spectrometry comprises fast-atomic bombardment mass spectrometry.
Preferably, said method of testing comprises polyacrylamide gel electrophoresis using an acid urea gel.
Preferably, said process includes the additional step of processing said milk into milk products.
There are a large number of processes known to those skilled in the art for converting milk into milk products. These range from separating cream from whole milk to produce skim milk through to the use of microfiltration and ultrafiltration to produce a wide range of products such as those described in international application PCT/NZ95/00086, the specification, claims and drawings of which are incorporated herewith by reference.
One particular product of interest from the aforementioned international application is milk protein concentrate. This may be prepared by other processes such as that described in IDF Special Issue No. 9201, (1991), Chapter 5 entitled xe2x80x9cMilk Protein Concentratexe2x80x9d, A. Novak.
Another milk product according to the invention is casein derived from non-diabetogenic milk by any well known casein producing process such as described in Southward et al, 1980.
The invention may be said broadly to consist in milk selected according to the process herein above defined.
The invention may also be said broadly to consist in a non-diabetogenic milk product prepared by any one of the processes described herein above.
The invention may also be said broadly to consist in a method for reducing the risk of contracting type 1 diabetes in a susceptible individual which comprises restricting the milk or milk product intake of that individual to milk containing only a non-diabetic variant of beta casein.
Preferably, said susceptible individual is an infant or young child.
The invention may also be said broadly to consist in a method of selecting milk for feeding to a Type-l diabetes susceptible individual which comprises testing milk from identified cows for the presence of the hexapeptide Pro-Gly-Pro-Ile-His-Asn (SEQ ID NO: 1), or a protein fragment containing the hexapeptide Pro-Gly-Pro-Ile-His-Asn (SEQ ID NO: 1) and selecting those cows whose milk does not contain said hexapeptide or said protein fragment containing said hexapeptide, and milking separately the cows whose milk does not contain the said hexapeptide or said protein fragment containing said hexapeptide and maintaining their milks separately from milk from any other source.
Preferably, said separated milk is also tested for the presence of said hexapeptide or said protein fragment containing said hexapeptide and any milk which does contain said hexapeptide or said protein containing hexapeptide is discarded.
Preferably, the method of testing for said hexapeptide is by using chromatographic purification of said hexapeptide followed by amino acid sequencing.
Preferably, said process includes the additional step of processing said milk into milk products.
The invention may be said broadly to consist in milk selected according to the process herein above defined.
The invention may also be said broadly to consist in a non-diabetogenic milk product prepared by any one of the processes described herein above.
Preferably, said susceptible individual is an infant or young child.
In another embodiment the invention may be said broadly to consist in a method for selecting breeding cows which produce daughters whose milk is not diabetogenic to susceptible children which comprises determining the genotype of said cows and selecting those whose daughters produce milk which does not contain the diabetogenic factor present in xcex2-casein.
Alternatively, the invention may be said broadly to consist in a process for selectively breeding bulls which produce daughters whose milk does not contain the diabetogenic factor present in xcex2-casein which comprises determining the genotype of said bulls and selecting those which daughters which produce milk which does not contain the diabetogenic factor present in xcex2-casein.
Preferably, the phenotyping of daughters to determine the genotype of said bull is done by testing the milk of said daughters for absence of diabetogenic variants of xcex2-casein and the presence of non-diabetogenic variants of xcex2-casein.
Alternatively, said cows or bulls are genotyped directly by using appropriate probes and polymerase chain reaction technology.
In another embodiment the invention may be said broadly to consist in cows selected in accordance with the immediately preceding method.
In a still further embodiment the invention may be said broadly to consist in bulls selected in accordance with the above defined method.
In a still further embodiment the invention may be said broadly to consist in semen of bulls selected in accordance with the above defined method.
In an alternative to any of the above processes or products the milk or milk product is goat""s milk or milk product, sheep""s milk or milk product, buffalo""s milk or milk product, or milk or milk product from any other mammal which is fit for human consumption.